Florida Gov. Rick Scott urged residents under evacuation orders as Hurricane Irma bears down on the state this weekend to get out immediately.

“We can rebuild your home … but you can’t get your life back,” said Scott.

The storm was increasingly likely to rip into heavily populated South Florida by early Sunday, prompting the governor earlier in the week to declare an emergency and officials to impose mandatory evacuation orders for parts of the Miami metro area and the Florida Keys, about 24 kilometres to the south of the Florida city.

About 100,000 in Miami-Dade County, many in low-lying areas, were subject to an evacuation order, with all hospitals in the Keys to be evacuated, in addition to residential areas.

“If you’re in the Keys and still home, leave and get out,” said Scott.

“The roads are going to going to get worse the longer you wait.”

Water levels in Lake Okeechobee and canals have been lowered, and the hope is the trajectory of the storm is faster moving than Harvey, which hit southeast Texas with up to 127 cm of rain and unprecedented floodwaters. Florida cities, according to current projections, see less than a quarter of that, but Scott said storm surge is still a big concern.

Residents line up for propane in Boca Raton, Fla., on Thursday. (REUTERS)

Florida Power and Light (FPL) said it had all hands on deck for Irma, but warned customers of the potential for prolonged outages. They urged people to prepare for that scenario, and said that in the worst-hit areas, the energy grid may need a rebuild.

Florida Highway Patrol troopers are monitoring the high volume of traffic heading north on the Turnpike as people leave South Florida ahead of Irma, which could make landfall in the state early Sunday morning.

In a news release Thursday, the highway patrol said extra troopers, road rangers and wreckers will be on the roadways to help drivers whose vehicles have become disabled.

The agency says disabled vehicles left on highway shoulders would be towed starting Thursday morning to make it easier for emergency workers trying to reach crash victims.

UPDATE: 20+ staging sites opening for thousands of workers who will restore power after #Irma . https://t.co/qGL0NceKjx

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@FPL_Newsroom

Turnpike officials are also using cameras along the road to monitor conditions.

As people head north and inward, the governor said 3,000 additional National Guard members are helping assist state troopers to prevent main arterial roads from coming to a standstill, but he urged drivers to exhibit patience in what will undoubtedly be a frustrating trek.

Fuel is also a concern, with Scott indicating the state will use all available resources to help escort gas trucks to stations and get fuel from port to land.

Feds, corporations pitch in

Scott said both President Donald Trump and Vice-President Mike Pence pledged to provide any necessary federal assistance, with the state in need of supply trucks, tarps, water and baby food, among other items.

He also said Google, Expedia and the U.S. telecom giants have stepped up to help provide up-to-date route conditions, non-shelter lodging information and free Wi-Fi areas.

Scott said the state is looking for an additional 10,000 volunteers — nearly double the current number who have signed up online or in person — to help move supplies and work at shelters.

Forecasters said Irma punish the entire Atlantic coast of Florida and rage on into Georgia and South Carolina.

“This could easily be the most costly storm in U.S. history, which is saying a lot considering what just happened two weeks ago,” said Brian McNoldy, a hurricane researcher at the University of Miami, alluding to the damage caused by Hurricane Harvey.

Scott warned earlier in the week that Irma is “bigger, faster and stronger” than Hurricane Andrew, which wiped out entire neighbourhoods in south Florida in 1992.

Until Hurricane Katrina over 12 years later, Andrew was estimated as the costliest storm in U.S. history, according to the National Weather Service.

South Florida has a better flood control system than in Texas — the ground is more porous and there aren’t any hills to send water rushing down from above, said Hugh Willoughby, a former research director at the National Oceanic and Atmospheric Administration (NOAA) and now a professor at Florida International University in Miami.

Georgia, Carolinas also monitoring

Still, many Floridians could find themselves with no money for flood repairs, just like people in Houston, where flood coverage dropped by nine per cent since 2012.

The latest forecasts suggest Irma’s most destructive winds could carve up much of Florida’s priciest real estate, damaging properties from all the way up to Jacksonville as it swirls north.

An Associated Press analysis shows a steep drop in flood insurance across the state, including the areas most endangered by what could be a devastating storm surge.

This June 7 file photo shows Peggy Wallace walking near her flooded neighbourhood in Davie, Fla. With Hurricane Irma bearing down on the state, an Associated Press analysis shows the number of federal flood insurance policies written in the state has fallen by 15 per cent. (The Associated Press)

With about 2,173 kilometres of coastline, the most in the continental United States, Florida has roughly 2.5 million homes in hazard zones, more than three times that of any other state, estimates the Federal Emergency Management Agency (FEMA). Yet across Florida’s 38 coastal counties, just 42 per cent of these homes are covered, with the state’s total number of federal flood insurance policies decreasing by 15 per cent in the last five years, according to FEMA.

If Irma’s eye follows a track just west of Florida’s eastern coast, the initial storm surge could heavily damage the Florida Keys, the cities at the southern tip of Florida’s mainland, Florida City and Homestead, parts of Miami and Miami Beach, and other Atlantic coast cities, said Brian Haus, a professor of ocean sciences at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science.

If Irma’s eye moves instead up Florida’s west coast, Tampa, St. Petersburg and other Gulf cities would be in danger of significant storm surge, Haus said.

Shifting forecasts have also prompted emergency declarations in the Carolinas and coastal Georgia, including areas that haven’t suffered a direct hit from a major hurricane in more than a century.

Georgia Gov. Nathan Deal declared a state of emergency Wednesday for the state’s 160-kilometre swath of Atlantic coast, which was last struck by a hurricane of force Category 3 or higher in 1898.

His South Carolina counterpart, Gov. Henry McMaster, declared an emergency for that neighbouring state as officials assessed the chances of receiving a major hurricane strike there for the first time in nearly 28 years.

McMaster cautioned it wasn’t yet an order of evacuation, but that could occur as early as Friday.

“When that hurricane is coming, when it gets close, it’s too late.”